1. Field of the invention
This invention relates to a method of recording and reproducing information in which information is recorded in and reproduced from a diskshaped information recording medium in sector units or on a sector by sector basis, and to an apparatus for performing the same.
2. Description of the prior art
In a conventional information recording and reproducing apparatus using an information recording medium (hereinafter, referred to as merely "a medium") such as a magnetic disk and floppy disk, the file management including the defective sector management is effected by using, for example, the MS-DOS (trademark) of Microsoft Corp. which is known as a general-purpose OS for a personal computer. In the MS-DOS, a directory area for recording management information and a data area for recording file data are formed on the medium. A file allocation table (FAT) area is also formed in the medium to record an FAT for controlling the status of the data area which is divided in cluster units. Each entry of the FAT (hereinafter, referred to as "an FAT entry") which corresponds to each of the clusters one by one manages the status information (used/unused) of each cluster and the linkage information of a plurality of clusters which are used in recording a file. In such a medium, a defective sector may occur due to flaws, contamination or deterioration of the recording material. When a cluster contains a defective sector, an identification flag is recorded in the FAT entry corresponding to the cluster, to manage such a defective sector. When a medium is formatted to initialize FAT entries, an unused flag meaning that a cluster is unused is recorded in FAT entries corresponding to clusters containing no defective sector, and a defect flag in FAT entries corresponding to clusters containing a defective sector. When recording a new file, FAT entries having the unused flag the number of which corresponds to the size of the new file are sequentially retrieved from the beginning of an FAT. In this operation, FAT entries having the defect flag are skipped so that defective sectors will not be used in recording the new file. After the data of the new file are recorded in unused clusters, the FAT is updated by rewriting the linkage information which describes the new status of the linkage of the clusters.
In a medium such as a write-once optical disk in which recorded information cannot be rewritten, the contents stored in one region of an FAT cannot be updated in the same region. Therefore, the aforedescribed management technique of a defective sector in a conventional file management system is not applicable to such a medium.
A medium such as a rewritable optical disk in which recorded information can be rewritten incurs a possibility that the occurrence of a defective sector may suddenly increase after the rewrite operation has been conducted tens or hundreds of thousands times. In such a medium, an FAT area is rewritten on each record or update operation so that the number of rewriting the FAT becomes extremely large, resulting in a greater possibility that a defective sector will occur in the FAT. However, a conventional file management system has no alternative means for a defective sector which may occur in an FAT area, thereby causing two FATs recorded to be recorded in a same FAT area. When a defective sector exists in an FAT area having an FAT, another FAT may be recorded in addition to the FAT, thereby causing both the FATs to be disabled for reproducing. Therefore, a conventional file management system using an FAT cannot be applied to an information recording medium such as a write-once optical disk or rewritable optical disk in which the number of rewriting information is limited.